The long-term objectives of the research ar to understand the function, regulation, and mechanism of action of a 16 kDa protein that is secreted in high amounts during pregnancy by the bovine uterine endometrium. The function of this protein has implications in several mammalian species, including humans, since it shares epitopes with ubiquitin and a 15-kDa ubiquitin cross-reactive protein (UCRP), and is regulated by conceptus- derived interferon tau (IFN-). Thus, this protein may serve as an index of early pregnancy and potentially, fertility. To meet the long-term objectives of the research, we intend to focus on the elucidation of structure and pregnancy-associated expression of the 16-kDa protein. Specifically, amino-terminal and internal peptide amino acid sequence will be determined following purification by using fast phase liquid chromatography. The cDNA(s) encoding the 16-kDa protein will be sequenced and used in Northern blots and in situ hybridization to confirm pregnancy-associated transcription. The number, complexity and distribution of genes across species will be studied by using Southern blots. A more specific polyclonal antiserum will be prepared and used to detect the 16-kDa protein in uterine secretions and serum. It also will be used to make an immunoaffinity matrix that will aid in purification. Immunosuppressive activity will be determined in rosette inhibition and anti-proliferative tests. Future experiments, by using cDNAs to generate recombinant 16-kDa protein, will be directed towards identifying function and mechanism of action during early pregnancy. Study of this 16-kDa protein has potential implication in human fertility, since communication between the conceptus and uterus is similar across many mammalian species.